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Influence of redox mediators and salinity level on the (bio)transformation of Direct Blue 71: kinetics aspects

Alvarez, Luis H., Meza-Escalante, Edna R., Gortáres-Moroyoqui, Pablo, Morales, Luz, Rosas, Krystal, García-Reyes, Bernardo, García-González, Alicone
Journal of environmental management 2016 v.183 pp. 84-89
azo dyes, chemical reduction, decolorization, humic acids, models, quinones, riboflavin, salinity
The rate-limiting step of azo dye decolorization was elucidated by exploring the microbial reduction of a model quinone and the chemical decolorization by previously reduced quinone at different salinity conditions (2–8%). Microbial experiments were performed in batch with a marine consortium. The decolorization of Direct Blue 71 (DB71) by the marine consortium at 2% salinity, mediated with anthraquinone-2,6-disulfonate (AQDS), showed the highest rate of decolorization as compared with those obtained with riboflavin, and two samples of humic acids. Moreover, the incubations at different salinity conditions (0–8%) performed with AQDS showed that the highest rate of decolorization of DB71 by the marine consortium occurred at 2% and 4% salinity. In addition, the highest microbial reduction rate of AQDS occurred in incubations at 0%, 2%, and 4% of salinity. The chemical reduction of DB71 by reduced AQDS occurred in two stages and proceeded faster at 4% and 6% salinity. The results indicate that the rate-limiting step during azo decolorization was the microbial reduction of AQDS.